Problem 54: Finish
Problem 54: Fix sort order when creating a HighCard instance; clean up main
Problem 54: Implement isFullHouse
Problem 54: Fix isFourOfAKind
Problem 54: Fix a bug in isThreeOfAKind, isTwoPairs, and isOnePair
Problem 54: Fix another bug in isTwoPairs
Problem 54: Tweak main
Problem 54: Remove some code that was commented out